This, or they are not trying to win through conventional means. Their strategy of winning elections in the future is to build a coalition of voters who will always vote D. Similar to how they were able to lock down the black vote since the 1960s through gibs, they want to apply this strategy to all immigrants. It is why they encourage immigration legal or otherwise so heavily. (Most of the republican party is in on this as well) The democrat party wants to simply win through demographic shift.
This is a scary proposition to anyone participating in a democracy. The candidates are no longer judged off of strength as a leader, rather just what political party they run for. George Washington made a speech on this in his
farewell address. This is how you get cases where a dementia riddled person is running for the most powerful elected office in the world. In my opinion, this strategy will eventually work.
The demographic shift strategy takes full effect when you have a bogeyman to run against. "Trump is evil, he wants to deport all immigrants" This is why I do not think the DNC minds losing as much this go around. Trump is the definition of evil according to many people on the left. Wait and pray for some major scandal to happen (see all their attempts at russia), then reap the benefits. Now they will have 4 more years to try and brand trump with some sort of scandal and hope it translates to a loss in 2024. By that time the demographic shift will be complete and the Republican party will have to completely abandon conservatism to stay relevant/electable nationally.